Percussion tone electrical musical instrument



Sept. 20, 1960 J. M. HANr-:RT

PERCUSSION TONE ELECTRICAL MUSICAL INSTRUMENT Filed March 15, 1957 om Q3M wn Nmfu 9 United States Patent O PERCUSSION TONE ELECTRICAL MUSICALINSTRUMENT John M. Hanert, Des Plaines, Ill., assignor to Hammond OrganCompany, Chicago, Ill., a corporation of Dela- Ware My invention relatesgenerally to electric musical instruments and more particularly to meansfor producing percussion tones by a monophonic or melody typeinstrument, or section of an instrument.

It is the primary object of the invention to provide means, for use inan electronic melody musical instrument, to cause the production oftones having percussion type intensity envelopes.

Other objects will appear from the following description, referencebeing had to the accompanying drawing which is a combined block andschematic circuit diagram illustrating the invention.

The instrument disclosed is a monophonic or melody instrument in whichthe pitch of the tone is controlled by an oscillator 10, comprisingtriodes 12 and 13, and tuned by a parallel resonant circuit, comprisinga capacitor C14 and one or more inductance elements or coils L16 whichare normally connected in series between the con-trol grid of triode 12and ground. The junctions between successive inductance elements L16 areconnected to switch contactors 18 operable by the playing keys 20 toconnect such junctions respectively to a grounded bus bar 22. In thismanner the value of the inductance in the resonant circuit for theoscillator is changed to tune the oscillator to the pitch correspondingto that of a depressed key, or to the pitch of the highest of a numberof keys operated at the same time.

In addition to operating the switch contactors 18, the playing keys4operate switch contactors 24 respectively to connect a bus bar 26 toground. The remaining elements of the oscillator 10 may be as shown inmy prior Patent No. 2,645,968, which also discloses the details of thefrequency dividers 30 and 32 which are coupled in cascade to the outputof the triode 13. Octave coupler switches 34, 35, 36, are adapted tocouple the output of the oscillator 10 and frequency dividers 30 and 32,respectively, to an amplifier 38. The output of the amplifier 3S isconnected across suitable tone control circuits 40 and across theprimary winding L42 of a transformer 44. The center-tapped secondary L46of this transformer has its end terminals connected to the control grids48 and 49 of a pair of control triodes S and 51. The outputs of thesetriodes are coupled by a transformer 52 to a high pass filtering mesh 54and to a normally open contactor 56 of a relay having a coil 58.

The center tap of secondary winding L46 is connected to ground through acapacitor C60 and is connected through the normally closed contactor 62of the relay and a relatively low value resistor R64, to a terminal 63of the power supply, the potential of which is sufficiently high toprovide normal operat-ing bias on the control triodes 50, 51. The centertap is also connected through a relatively high value resistor R66 to aterminal 68 of the power supply which has a negative voltagesufliciently low to cut off the triodes 50, 51.

The relay coil 58 has one end connected to a B+ terminal of the powersupply and its other end connected to the plate of a triode 70. Thecontrol grid of the triode 70 is connected to the terminal 72 of thepower supply at which the voltage is sufiiciently negative to maintainthe triode 70 at cutoff, `this connection being made through a gridresistor R74. 'l`he contactor 56 of the relay is adapted to connect theoutput conductor 55 to the input conductor 76 of an amplifier 78, whichis coupled to a speaker 80. The conductor 76 is connected to groundthrough a suitable key click suppression mesh comprising a capacitor C82and resistor R84 connected in parallel.

It should be noted that the switch contactors 18 and 24 are mechanicallyconnected to their associated keys in such manner so that upondepression of the key the switch l18 will close before the switch 24 isclosed. This sequence is very desirable so that any transients producedupon changing the frequency of the oscillator 10 by closure of a switch18 will not be transmitted to the amplifier 78.

In operation, assuming one or more of the switches 34, 35, 36 is closed,depression of the key will first, by closure of its associated switch18, tune the oscillator 10 to a frequency corresponding to, or `octavelyrelated to, the nominal pitch of the depressed key. The frequencydividers 30 and 32 are operable successively to divide the frequency atwhich the oscillator 10` operates by two and thus the tones are octavelyrelated. The signals from the oscilla-tor and one or both of thefrequency dividers 30 and 32 may be transmitted to the amplifier 38 andthus through the transformer 44 to the input of control tubes 50 and 51.The relative values of resistors R64 and R66 is such that the normalbias voltage is applied through the center tap on transformer secondaryL46 through the switch 62 and thus this bias appears on the controlgrids 48 and 49 of triodes 50 and 51, and these triodes are in conditionto transmit the signal supplied by the oscillator and frequencydividers.

Thus, upon initial depression of a playing key its switch 18 andassociated circuits tune the oscillator 10 to the required frequency.The signal output of the oscillator 10 and dividers 30, 32, is nottransmitted to the amplifier 78 because the switch contactor 56 of therelay 58 is open. However, upon further depression of the playing keythe switch 24 associated therewith will be closed and the triode 70,which is normally not conducting, because of the relative cutoff biasvoltage present on its control grid, has its control grid connected toground through the operated switch 24. Thus, the triode 70 conducts andthe relay 58 is energized, the switch contactor 62 opened, and 56closed. Upon closure of switch 56 the signals, as amplitude controlledby the control tubes 50, 51, is impressed upon the input circuit of theamplifier 78 and translated into sound by the speaker 80. The controlgrids 48 and 49 are normally held at operating potential when the switchcontactor 62 is closed, but when this switch is opened the charge on thecapacitor C60 is dissipated at a rate depending upon the time constantof capacitor C60 and resistor R66. This time constant is preferably madevery short so that the tone intensity will decay rapidly in the mannerof the tones of percussive musical instruments such as the piano (asplayed when the sustaining pedal is not depressed), Xylophone, andsimilar instruments of the percussion group.

Upon release of the key the signal is rst removed from the amplifier 78by the opening of 56 due to the fact that the grid of the triode 70 israpidly reduced to the cutoff potential, deenergizing relay 58. Suchdeenergization and closure of contactor 62 results in again applying anormal operating biasing voltage to the capacitor C60, recharging thecapacitor C60, and conditioning the percussion control means foroperation upon depression of a second key.

The keys are played in a detached or staccato manner so that capacitorC60 is quickly recharged between the playing of successive notes.

While I have shown and describeda particular embodiment of my invention,it will be apparent to those skilled in the art that numerousmodifications and variations may be made in the form and constructionthereof, without departing from the more fundamental principles of theinvention. -I therefore desire, by the following claims, to includewithin the scope of my invention all such similar and modiied forms ofthe apparatus disclosed, by which substantially the results of theinvention may be obtained by substantially the same or equivalent means.

I claim:

1. In an electrical musical instrument, the combination of acontinuously operating electrical musical tone signal generating means,a plurality of playing keys, an output system, means operated by partialdepression of the playing keys to cause transmission of tone signals ofpitch corresponding to the nominal pitch of the operated key from thegenerator to the output system, said output system including toneintensity envelope controlling means, a relay having normally closedswitch contacts and normally open switch contacts, switches respectivelyoperable by the keys to cause completion of a circuit to energize therelay, circuit means including the normally closed relay switch tomaintain the tone intensity control means in condition for transmissionof the signal at high amplitude, an amplifier and speaker connectedthereto, circuit means including the normally open switch of the relayoperable when the relay is energized to connect the output o-f the toneintensity controlling means to the amplifier, and means renderedeffective by `the opening of the normally closed switch to cause theintensity envelope control means to transmit the signal at progressivelydecreasing amplitude.

2. The combination set forth in claim 1 in which the switches areoperated by the keys when the keys are ysubstantially fully depressed.

3. rllhe combination set yforth in claim 1 in which the relay energizingcircuit means includes an electron discharge amplifying device.

References Cited inthe tile of this patent UNITED STATES PATENTS2,233,258 Hammond et al. Feb. 25, 1941 2,301,871 Hanert Nov. 10, 19422,310,429 Hanert Feb. 3, 1943 2,357,191 Hanert Aug. 29, 1944

